Rotary abrasive device

ABSTRACT

A rotary abrasive device in which abrasive units are replaceably mounted on a powered mandrel, the units including retainer members insertable endwise into grooves in the mandrel; the configuration and relationship of the retainer members and peripheral openings of the grooves, and attachment of the retainers to abrasive packs with a spacing between the base edges of the packs and the surface of the mandrel, affording a limited pivotal movement of the retainer members and packs.

United States Patent Burns Jan. 16, 1973 54 ROTARY ABRASIVE DEVICE 2,871,632 2/1959 Cosmos ..51/337 V. a I 3,349,423 10/1967 L sb r ....lS I83 [75] Inventor: Russell W. Burns, Topanga, Calif. 3141269 7/1964 3,165 5J3 90290 3,455,068 7/1969 Belanger ..5l/337 [73] Assignee: Merit Abrasive Products, Inc.,

Compton, Calif. Primary Examiner-Othell M. Simpson Att0meyHuebner & Worrel [22] Filed: April 9, 1971 [21] Appl. No.: 132,889 ABSTRACT Related US. Application Data [62] Division of Ser No 817 773 A r M 1969 Pat A rotary abrasive device in which abrasive units are NO 3 619 948 p replaceably mounted on a powered mandrel, the units including retainer members insertable endwise into 52 u.s.(:l..... ..s1/334 gmoves mandrel; configuration and F613 51 Int. Cl. ..B24b 9/02 timship of the retainer members Peripheral [58] Field of Search "51/334431 Penings moves and attachment of 5 179 1 1 23943016 retainers to abrasive packs with a spacing between the 1 l base edges of the packs and the surface of the man- [56] References Cited drel, affording a limited pivotal movement of the retainer members and packs. UNITED STATES PATENTS 2,423,992 7/1947 Nordgren et al. ..5l/334 5 Claims, 15 Drawing Figures PATENTED JAN 16 I973 SHEET 1 BF 4 PATENTEDJM 16 mm 3. 7'1 1. 261

SHEET 2 OF 4 Vi Z 90 22 Arron/M4 ROTARY ABRASIVE DEVICE CROSS-REFERENCE TO RELATED APPLICATION The present application is a division of application Ser. No. 817,773 filed Apr. 21, 1969 for Internally Powered Rotary Abrasive Means now US. Pat. No. 3,619,948.

BACKGROUND OF THE INVENTION The invention is directed to the solution of a number of problems which arise in different uses of power actuated rotary mandrels that are equipped with radial arrays of abrasive elements to abrade different objects for different purposes. Such rotary abraders include devices for processing workpieces for various purposes and further include large rotary abraders for continuously removing adherent material from the surfaces of work rolls that are employed for hot rolling sheets of aluminum or the like.

Compactness in axial dimension is desirable and especially so in abrading devices used in industry where either a motor or a belt-driven pulley is typically positioned at one end of the mandrel to actuate the mandrel.

For a number of reasons, the need for achieving compactness is especially pressing in the large rotary abrasive devices that are used for removing adherent material from the work rolls in a rolling mill. One reason is that the rotary abrader must process a full width of the associated work roll and, therefore, must completely span the space that is available between the two heavy support structures in which the opposite ends of the work roll are journaled. If a drive motor or drive pulley is employed in this available space at one end of the mandrel, the axial dimension of the mandrel must be correspondingly reduced. On the other hand, if the motor or pulley is placed outside this available space, other troublesome difficulties arise.

The problem of axial compactness may be met by using a-hollow mandrel and simply incorporating a motor into the interior of the hollow mandrel. For a number of reasons, however, this solution has not been carried out. The most serious difficulty is that considerable heat is generated by the abrading action on the workpiece and this heat is transmitted by the abrading elements to the mandrel. The heat generated by the workpieces is usually dissipated by a conventional mandrel at an acceptable rate, but if a motor is mounted inside the mandrel, the internally created heat is added to the externally created heat to result in a total heat load that is beyond the usual heat-dissipating capacity of a mandrel.

It would seem that the problem of cooling the interior of the hollow mandrel could be solved by increasing the inner diameter of the mandrel to provide room for the internal motor and to provide additional room for a high volume of cooling airflow through the mandrel. This solution is not widely acceptable because it means too great a departure from the optimum diameter of a mandrel. Also if a hollow mandrel is to be used in a space of limited diametrical dimension, increasing the diameters of the mandrel means correspondingly decreasing the length of the radial abrasive elements. The radial abrasive elements must be relatively long, however, both for the sake of efficient abrasive action and for the sake of adequate service life for the abrasive elements.

The present invention is directed to these various problems.

SUMMARY OF THE INVENTION The invention makes it possible to use an internally powered mandrel of relatively small diameter by giving the mandrel a configuration that provides a self-cooling action. For this purpose, the mandrel is provided with peripheral recesses that not only increase the area of the mandrel for increased heat transfer to the atmosphere, but also create air turbulence and air eddies for additional cooling effect. In addition, the recesses form ribs on the periphery of the mandrel that not only create additional turbulence in the boundary layer of air, but also function as heat-radiating fms. The invention teaches that such ribs may either extend longitudinally of the mandrel or circumferentially of the mandrel.

The invention further teaches that both highly effective abrasive action and improved ambient air circulation for overall cooling effect on the mandrel may be achieved by using flap-type abrasive elements. The abrasive elements are flexible leaves arranged in packs with the packs extending generally lengthwise of the mandrel. Unfortunately, however, in such a construction the successive packs of leaves slap a workpiece with repeating hammering effect that produces undesirable slap marks on workpieces.

It has been discovered that the hammering effect is accentuated when the mandrel is mounted in the usual manner on a drive shaft driven through the usual universal joint. The hammering effect is transmitted through the universal joint and is reflected or fed back to the mandrel.

The invention reduces this hammering effect to insignificance by two provisions. The first provision is to put the actuating motor inside the hollow mandrel to eliminate the feedback. The second provision is to give the spaced longitudinal packs of leaves a spiral curvature on the periphery of the mandrel. By virtue of the spiral curvature, each longitudinal pack contacts a workpiece progressively along the length of the pack with a wiping action instead of the whole length of the pack making simultaneous impact against the workpiece.

With reference to the desirability of keeping the cylindrical wall of the mandrel relatively thin thereby to make it possible to use relatively long radial abrasive leaves in a limited space, the invention teaches that the peripheral recesses of the mandrel may be formed with overhanging shoulder and that suitable retainer means for attaching the abrasive packs to the mandrel may be adapted to releasably engage the overhanging shoulders. With the overhanging shoulders located close to the periphery of the mandrel, the cylindrical wall may be thin because only a shallow depth of the mandrel is needed to anchor the abrasive packs. The invention further teaches that a shallow depth of anchorage may be made possible by relying largely on centrifugal force to maintain the desirable radial positioning of the packs of leaves.

In the preferred practice of the invention the peripheral recesses with the overhanging shoulders are open to the opposite ends of the mandrel and consequently additional cooling air turbulence is created at the opposite ends of the mandrel. In this regard, a

further feature of the invention is that the retainer means that extend into the recesses for anchorage of the abrasive packs are dimensioned for clearance in the recesses and the clearance spaces in the recesses provide additional cooling ventilation.

The provision of peripheral recesses in the mandrel both for air cooling and for anchorage of the abrasive packs necessarily means removal of some of the metal of the mandrel. The invention teaches, however, that the retainer means employed to anchor the packs of abrasive leaves to the mandrel may include metal rods or the like that extend through the recesses from end to end of the mandrel, the metal rods at least partially compensating for the metal that is sacrificed in the forming of the recesses.

Since the mandrel is internally driven, both ends of the mandrel are free to receive a loading. In other words,.the loading may be inserted on the mandre] from either end. This is advantageous over the prior art since the disposition of the motor at one end of the mandrel has prevented the loading from being inserted on the mandrel at that end of the mandrel.

The features and advantages of the invention may be understood from the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which are to be regarded as merely illustrative:

FIG. I is a longitudinal sectional view showing the presently preferred embodiment of an internally powered rotary flap-type abrasive device;

FIG. 2 is an end elevation of the device as seen along the line 22 of FIG. 1;

FIG. 3 is an enlarged end view of an abrasive unit comprising a pack of abrasive leaves mounted on a retainer member that is adapted for releasable engagement with the mandrel;

FIG. 4 is a diagrammatic view showing how a keyhole slot of generally triangular configuration may be cut in a mandrel;

FIG. 4a is a similar view showing how an end mill cutter may be employed to cut such a slot;

FIG. 5 is a diagrammatic view showing how the end mill cutter of FIG. 4a may be employed to cut spiral slots in the periphery of a mandrel;

FIG. 6 is a greatly enlarged portion of FIG. 2 indicating how the mandrel is cooled by air turbulence and circulation;

FIG. 7 is a view similar to FIG. 6 showing how substantially the same air circulation and turbulence are created if the keyhole slots are of generally circular configuration;

FIG. 8 is an end elevation of an abrasive unit employed in a second embodiment of the invention;

FIG. 9 is a fragmentary perspective view showing how the periphery of the mandrel of the second embodiment of the invention is recessed for cooling action and for releasably mounting the abrasive units;

FIG. 10 is a side elevation of one of the packs of abrasive leaves shown in FIG. 8;

FIG. II is an enlarged fragmentary perspective view of a retainer member for a pack of abrasive leaves;

FIG. 12 is an end elevation of the second embodiment of the invention;

FIG. 13 shows how the keyhole slots in FIG. 9 may be arranged in helically curved rows; and

FIG. 14 is a fragmentary perspective view similar to FIG. 9 in which the keyhole slots are of generally circular cross-sectional configuration.

DESCRIPTION OFTHE PREFERRED EMBODIMENTS OF THE INVENTION In the first embodiment of the invention shown in FIGS. 1, 2, 3 and 6, the mandrel comprises a cylindrical shell 20 that is rotatably mounted on fixed structure that extends through the shell axially thereof. The fixed structure comprises an inner cylinder 22 having end walls 24 that are formed with tubular axial extensions 25. As indicated in FIGS. 1 and 2, each of the two opposite axial extensions 25 is fixedly engaged by support means in the form of a corresponding stanchion 26, the tubular extension being seated in an aperture 28 of the stanchion and being releasably anchored therein by a set screw 30. The opposite ends of the cylindrical shell 20 are rotatably mounted on the corresponding tubular extensions 25 by corresponding ballbearings having outerraces 32 and inner races 34. Each of the outer races 32 is backed against an inner circumferential shoulder 35 of the cylindrical shell and is retained by a suitable snap ring 36. In like manner, each of the inner races 34 backs against a circumferential shoulder 38 of the corresponding tubular extension 25 and is secured by a snap ring 40.

A suitable motor 42 is mounted by radial supports 44 inside the inner shell 22 with an annular clearance 45 around the motor. One end of the shaft 46 of the motor carries a centrifugal blower 48 having a circumferential set of blades 50 and the other end of the shaft drives reduction gearing in a gear box'52 having an output shaft 54. A suitable pinion on the output shaft extends through a window 56 of the inner shell 22 and meshes with the internal teeth of a ring gear 57 that is fixedly mounted on the inner circumference of the cylindrical shell 20. It is apparent that the centrifugal blower 48 draws a stream of air through the adjacent tubular extension 25 and forces the stream of air through the annular clearance 45 around the motor with the stream of air discharging into the atmosphere through the second tubular extension 25 at the opposite end of the mandrel. The wiring 58 for the motor may extend through one of the tubular extensions 25 to an external source of EMF.

Further forced air circulation through the interior of the mandrel may be provided through the annular space 59 between the outer cylindrical shell 20 and the inner cylinder 22. For this purpose helical vanes 60 may be fixedly mounted on the inner circumferential surface of the cylindrical shell 20 on opposite sides of the ring gear 57 and air passage bores 61 may be provided in the inner races 24 of the ballbearings.

As indicated in FIG. 1 the abrasive elements carried by the mandrel comprise a radial array of abrasive leaves which are coated with highly abrasive particles in a well known manner. As indicated in FIG. 1 sheets generally designated 62 of the flexible abrasive material may extend longitudinally of the mandrel, each sheet having a series of spaced slits 64 that divide the sheet into individual abrasive leaves 65. As indicated in FIG. 3 a pack 66 of the sheets 62 is mounted on a suitable retainer member that is adapted for releasable engage: ment with the mandrel, the retainer member having a longitudinal enlargement 68 for engaging the mandrel and having a web 70 that extends into the pack of leaves and is attached thereto by suitable means such as a series of staples 72. In the particular construction shown in FIG. 3 the retainer member comprises a sheet of flexible material which is folded to provide two layers for the web 70 and to enclose a metal rod 74 to form the enlargement 68.

As heretofore stated, the invention teaches that the periphery of the mandrel or cylindrical shell may be suitably recessed for the dual purpose of making the mandrel self-cooling and of providing means for releasably engaging the various retainer members. In this first embodiment of the invention the mandrel is formed with a series of longitudinally extending peripheral recesses or slots 75 which are spaced circumferentially of the mandrel and which may be described as of a keyhole cross-section configuration in that each slot has a peripheral opening or entrance that is narrower in width than the maximum width dimension of the slot.

In this instance, as best shown in FIG. 6, each slot 75 is of generally triangular configuration with inwardly inclined overhanging side walls 78 and with a restricted peripheral opening or entrance 80. As shown in FIG. 6 the enlargement 68 of each retainer member is rotatably or pivotally captivated by the corresponding slot 75, curved concentric surfaces of the enlargement being in contact with the overhanging side walls 78. It is apparent that a retainer for a pack 66 of abrasive leaves may be made entirely of metal or may be a one-piece plastic member.

Hingedly mounting each of the abrasive packs 66 on the mandrel 20 in the described manner permits the abrasive units to swing through a liberal range of angles relative to the mandrel and thus permits the individual abrasive units to be urged effectively by centrifugal force to the desired radial positions for abrasive operation.

The self cooling action of the mandrel will now be explained.

As may be seen in FIG. 2, the successive slots 75 form longitudinal ribs 82 on the mandrel which act as cooling fins for heat dissipation by radiation. In addition, the slots 75 create air circulation, air turbulence and air eddies for cooling action on the mandrel and on the inner ends of the radial packs 66. As may be seen in FIG. 6 centrifugal force urges the packs 66 radially outward to create liberal clearance spaces for air circulation between the inner ends of the packs and the periphery of the mandrel. In addition, it is to be noted in FIG. 6 that the enlargement 68 of a retainer member is of substantially less cross-sectional area than the cross section of the corresponding slot 75 to result in liberal clearance space for air circulation within the slot. Since each of the slots 75 opens onto the two opposite ends of the mandrel, there is freedom for airflow through the slots from end to end and in addition the open ends of the slots create turbulence and air eddies at the opposite end surfaces of the mandrel.

FIG. 7 indicates that the same kind of self cooling action is created if the mandrel is provided with slots 75a of generally circular cross-sectional configuration instead of generally triangular cross-sectional configuration. The slots a have curved overhanging side walls 78a and restricted peripheral entrances 80a.

At this point it is appropriate to explain how the invention permits the use of relatively long abrasive leaves 65 on a mandrel which must operate in a limited space.

Since centrifugal force is relied upon to urge the packs 66 to their desired radial positions, it is not necessary for the mandrel to cooperate mechanically with the retainer members to hold the packs in the radial positions. For this reason, the recesses or slots 75 may be relatively shallow, the abrasive units in effect having relatively short roots in the mandrel so that only a relatively thin outer peripheral portion of the mandrel is required for anchorage of the abrasive units. Consequently, as far an anchorage of the abrasive units is concerned, the shell 20 may be relatively thin. In fact the shell may be only as thick as required for adequate structural strength. In this regard it is to be noted that although metal is removed from the mandrel to form the slots 75, nevertheless partial compensation for the removed metal is provided for the metal rods 74 of the retainer members.

Since the cylindrical shell 20 is self-cooling by reason of the recesses and ribs, the cylindrical shell may be of relatively small diameter for a motor of a given diameter. The smaller the diameter of the shell and the thinner the shell, the longer the abrasive leaves 65 may be to operate in a space that is limited to a given diametrical dimension. The abrasive means constituting this invention are also advantageous in that the abrasive packs may be located on the mandrel from either end of the mandrel.

FIG. 4 shows how a keyhole slot 75 may be cut in a cylindrical shell 22 by a series of three milling cutters 84, and 86. First the milling cutter 84 of the configuration shown is employed to cut the peripheral entrance to the slot and to form a portion of the slot proper, then the second milling cutter 85 which is of the shape shown in FIG. 4 is employed to cut away an additional portion of the slot, the result of these two cutting actions being the formation of a triangular rib 88 of residual metal in the bottom of the slot. The third milling cutter 86 which is of the configuration shown in FIG. 4 is then introduced into the slot to remove the residual rib 88.

FIG. 4a indicates how an end mill 89 may be employed to cut a slot 75. The end mill 89 has a conical cutting head 90 and has a shank 92 that also has cutting edges. Thus the conical head 90 cuts the slot proper and the shank 92 cuts the entrance 80 of the slot.

As heretofore stated, the hammering effect of the slapping action of the packs 66 against a workpiece, may be minimized if not entirely eliminated by the two provisions of, first mounting the motor inside the mandrel and, second, curving the packs 66 helically with respect to the periphery of the mandrel. For this purpose, the slots 75 may extend helically of the mandrel and the retaining members of the packs 66 may be either pre-curved to helical configuration or may be sufficiently flexible to conform to the helical configuration of the slots.

FIG. 5 shows diagrammatically how a cylindrical shell 20a may be mounted on a lathe for closely controlled rotation and the previously described end mill 89 may be mounted on a head 94 that actuates the end mill and is movable at a controlled rate along a linear guideway 95. The rate of rotation of the cylindrical shell and the rate of travel of the head 94 may be at whatever ratio is required for forming slots 75 of a given helical configuration.

In the first described embodiment of the invention the heat-radiating fins are longitudinal ribs and if the slots are helically curved the longitudinal ribs are helically curved. In the embodiment of the invention shown in FIGS. 8 to 12, the cooling fins are circumferential ribs as distinguished from longitudinal ribs.

In FIG. 9 the recesses in the mandrel 20b include circumferential grooves 96 that form circumferential ribs 98 and the recesses further include keyhole slots 100 of generally triangular cross-sectional configuration in the ribs 98, the keyhole slots being aligned in rows longitudinally of the mandrel. The manner in which abrasive packs 66b of the construction shown in FIG. 8 may be releasably mounted on the mandrel 20b may be understood by reference to FIGS. 10, 11 and 12.

FIG. 11 shows a retainer member made of suitable sheet material, which may be sheet metal or may be plastic, the sheet material being folded to form two spaced webs 102 and the material of the sheet material being cut away to form a series of retainer loops 104 that are spaced and dimensioned to extend into the circumferential grooves 96 of the mandrel 2019. As shown in FIG. 8, the two webs 102 of the retainer member shown in FIG. 11 are sandwiched between leaves of the pack 66a. Suitable fastening means in the form of staples 105 anchor the abrasive leaves to the webs 102, the staples being spaced longitudinally of the pack as may be seen in FIG. 10. With the retainer loops I04 of a pack 66a extending into the circumferential grooves 96 of the mandrel 20b and with the retainer loops aligned with a row of the keyhole slots 100, a retainer rod 106 may be inserted from one end of the mandrel and threaded through the successive keyhole slots and through the retainer loops to anchor the pack to the mandrel.

It is apparent that in this second embodiment of the invention as in the first embodiment, since the packs are pivoted to respond to centrifugal force only a shallow depth of the periphery of the mandrel is required for anchorage of the abrasive packs. A feature of this second embodiment is that the keyhole slots 75a are very short and open onto opposite sides of the circumferential ribs 98 for even more freedom for air circulation than is provided by the first embodiment. Here again air circulation through the keyhole slots 75a is promoted because the triangular configuration of the slots provides liberal clearance around the retainer rods 106.

ferential grooves 96 forming circumferential ribs 98,

My description in specific detail of the selected embodiments of the invention will suggest various changes, substitutions and other departures from my disclosure.

I claim:

1. In a rotary abrasive device which comprises an annular mandrel formed with generally longitudinal peripheral grooves open at at least one end for the reception of an abrasive unit retainer, a plurality of abrasive units each comprising a pack of abrasive leaves and a retainer secured to the pack, the retainer being replaceably mounted in a groove, the improvementwhich comprises: said grooves each having a cross sectional area of predetermined measurement, the walls defining the groove converging to form a constricted opening at the periphery of the mandrel and terminating at said periphery in opposite generally sharp edges, the abrasive unit retainers each comprising a web having a cross sectional dimension less than that of the peripheral opening of the groove, an enlargement extending inwardly from the web and having a transverse cross section greater than that of said peripheral opening, the web extending outwardly through said peripheral opening from the periphery of the mandrel a sufficient distance and its securement to the abrasive pack being such as to provide a spacing between the periphery of the mandrel and the adjacent edge of the pack, whereby the retainer may havea limited pivotal movement in the groove transmitted to the pack.

2. A device as defined in claim 1 in which the grooves have the general form of dovetail slots, and the enlargements of the retainer are generally annular in cross section.

3. A device as defined in claim 1 in which the grooves have an interrupted annular cross sectional form, and the enlargements of the retainer are generally annular in cross section.

4. A device as defined in claim 2 in which the radial depth of the grooves is greater than the radial dimension of the enlargements whereby space for circulation of air through the grooves is provided.

5. A device as defined in claim 3 in which the diameter of the grooves is greater than the diameter of the enlargements whereby space for circulation of air through the grooves is provided. 

2. A device as defined in claim 1 in which the grooves have the general form of dovetail slots, and the enlargements of the retainer are generally annular in cross section.
 3. A device as defined in claim 1 in which the grooves have an interrupted annular cross sectional form, and the enlargements of the retainer are generally annular in cross section.
 4. A device as defined in claim 2 in which the radial depth of the grooves is greater than the radial dimension of the enlargements whereby space for circulation of air through the grooves is provided.
 5. A device as defined in claim 3 in which the diameter of the grooves is greater than the diameter of the enlargements whereby space for circulation of air through the grooves is provided. 